1. Field of the Invention
This invention relates to a novel and improved fluid-tight, durable metal enclosure for a geophone electrically connected to a cable. In particular, this invention relates to a fluid-tight metal enclosure adapted for use in the seismic industry as a fluid-tight, durable metal enclosure for enclosing a seismometer for detecting seismic waves produced by a seismic energy source in marshes, swamps and other damp and wet geographical locations.
2. Disclosure of the Prior Art
It is known in the prior art to use fluid-tight, high impact polycarbonate (Lexan) cases to enclose or house a geophone which is electrically connected to a cable which passes through the case. Use of a knot-anchored takeout to prevent withdrawal of the cable from the case and disconnection of the cable from the geophone is known and described in U.S. Pat. No. 3,119,978. Known applications using a knot-anchored takeout include a land case or a marsh case wherein the entire case is formed of plastic. In the land case, the top of the case is removable. The removable top is joined to the case with a threaded screw ring or a slip-on ring. Entry of the cable into the case is through the threaded screw or slip-on ring. If desired, the interior of the case can be filled with a silastic material to encapsulate the geophone, cable, the knot-anchored takeout and the electrical connections between the cable and geophones. In the marsh case, the entire case is either an integral housing formed around the geophone and cable or is formed of several major segments which are mechanically joined by a metal band or other fastening means.
The prior art cases have several disadvantages. One disadvantage is that under continuous usage, the water proof seal between the plastic housing and top or housing segments may leak. The plastic material itself is subject to deterioration from sunlight and temperature extremes. In addition, potting components, such as silastic, may be required. Field servicing and repair is sometimes time consuming, difficult and requires special tooling. In some types of cases, the geophone itself may rotate within the case when the case is subjected to rotational force or abrupt movements. The geophone rotation has been known to disrupt, short or otherwise affect the electrical connection between the cable and geophone terminals.